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Title: Defect-band mediated ferromagnetism in Gd-doped ZnO thin films

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 117; Journal Issue: 1; Related Information: CHORUS Timestamp: 2016-12-21 06:44:04; Journal ID: ISSN 0021-8979
American Institute of Physics
Country of Publication:
United States

Citation Formats

Venkatesh, S., Franklin, J. B., Ryan, M. P., Lee, J. -S., Ohldag, Hendrik, McLachlan, M. A., Alford, N. M., and Roqan, I. S. Defect-band mediated ferromagnetism in Gd-doped ZnO thin films. United States: N. p., 2015. Web. doi:10.1063/1.4905585.
Venkatesh, S., Franklin, J. B., Ryan, M. P., Lee, J. -S., Ohldag, Hendrik, McLachlan, M. A., Alford, N. M., & Roqan, I. S. Defect-band mediated ferromagnetism in Gd-doped ZnO thin films. United States. doi:10.1063/1.4905585.
Venkatesh, S., Franklin, J. B., Ryan, M. P., Lee, J. -S., Ohldag, Hendrik, McLachlan, M. A., Alford, N. M., and Roqan, I. S. 2015. "Defect-band mediated ferromagnetism in Gd-doped ZnO thin films". United States. doi:10.1063/1.4905585.
title = {Defect-band mediated ferromagnetism in Gd-doped ZnO thin films},
author = {Venkatesh, S. and Franklin, J. B. and Ryan, M. P. and Lee, J. -S. and Ohldag, Hendrik and McLachlan, M. A. and Alford, N. M. and Roqan, I. S.},
abstractNote = {},
doi = {10.1063/1.4905585},
journal = {Journal of Applied Physics},
number = 1,
volume = 117,
place = {United States},
year = 2015,
month = 1

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4905585

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Cited by: 13works
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  • Gd-doped ZnO thin films prepared by pulsed laser deposition with Gd concentrations varying from 0.02–0.45 atomic percent (at. %) showed deposition oxygen pressure controlled ferromagnetism. Thin films prepared with Gd dopant levels (
  • The room temperature ferromagnetism recently discovered in transition metal doped oxides makes of them unique materials for new spintronic technologies. However, the mechanism responsible for this behavior has remained elusive. Here we use Z-contrast scanning transmission electron microscopy to image the Co and find that the magnetic phase in Co doped TiO2 films consists of a superstructure of interstitial Co atoms homogeneously distributed in the anatase lattice. Detailed analysis of the energy-loss near edge structure at the Ti L2,3 edge shows that the activation of ferromagnetism by post growth vacuum annealing involves the creation of Co - Ti3+- oxygen vacancymore » defect complexes. First-principles, spin-polarized density functional theory calculations confirm that these defect complexes have the lowest energy configuration and that their magnetic moment is in agreement with experimental observations.« less
  • We have introduced defects in ZnO (undoped and doped with Co and Mn) epitaxial thin films using laser irradiation from nanosecond laser pulses and thermal annealing in oxygen ambient. In contrast to the as grown samples, the laser irradiated films show a significant increase in conductivity, enhancement in UV emission, while maintaining the same wurtzite crystal structure. Room-temperature ferromagnetism (RTFM) is observed in laser-irradiated samples, which increased with the number of laser pulses up to a certain value where magnetic moment saturates. The induced ferromagnetism as well as the enhanced electrical conductivity can be reversed with thermal annealing in oxygenmore » ambient. The magnetization in Co and Mn doped films was found to be strong function of growth conditions and defect concentration. X-ray diffraction and optical absorption experiments suggested a 2+ valance state and tetrahedral coordination for both Co and Mn ions. There is a simultaneous increase in n-type electrical conductivity with the number of laser pulses and continue to exhibit semiconducting behavior in both undoped and doped films. The saturation magnetization was found to be 0.08 {mu}{sub B}/Co and 0.05 {mu}{sub B}/Mn, much lower than 3.0 {mu}{sub B}/Co and 5.0 {mu}{sub B}/Mn, indicating the prominent role of intrinsic defects in RTFM with some contribution from Co{sup 2+}-oxygen vacancy complexes. We propose a unified mechanism based upon introduction of intrinsic defects to explain RTFM and n-type conductivity enhancements during pulsed laser and thermal annealing.« less
  • We demonstrate the fabrication of reproducible long-range ferromagnetism (FM) in highly crystalline Gd{sub x}Zn{sub 1−x}O thin films by controlling the defects. Films are grown on lattice-matched substrates by pulsed laser deposition at low oxygen pressures (≤25 mTorr) and low Gd concentrations (x ≤ 0.009). These films feature strong FM (10 μ{sub B} per Gd atom) at room temperature. While films deposited at higher oxygen pressure do not exhibit FM, FM is recovered by post-annealing these films under vacuum. These findings reveal the contribution of oxygen deficiency defects to the long-range FM. We demonstrate the possible FM mechanisms, which are confirmed by density functionalmore » theory study, and show that Gd dopants are essential for establishing FM that is induced by intrinsic defects in these films.« less
  • Origin of unexpected defect engineered room-temperature ferromagnetism observed in tin-doped indium oxide (ITO) nanostructures (Nanowires, Nano-combs) and nanocrystalline thin films fabricated by pulsed laser deposition has been investigated. It is found that the ITO nanostructures prepared under argon environment exhibit strongest ferromagnetic signature as compared to that nanocrystalline thin films grown at oxygen. The evidence of singly ionized oxygen vacancy (V{sub 0}{sup +}) defects, obtained from various spectroscopic measurements, suggests that such V{sub 0}{sup +} defects are mainly responsible for the intrinsic ferromagnetic ordering. The exchange interaction of the defects provides extensive opportunity to tune the room-temperature d{sup 0} ferromagnetismmore » and optical properties of ITOs.« less